DNA With A Grasp For Uranium

A new uranium sensor that's both portable and exquisitely sensitive could transform how scientists assess and monitor the radioactive element (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.0607875104). The system will be important in environmental remediation efforts, according to chemistry professor Yi Lu of the University of Illinois, Urbana-Champaign, who spearheaded the research. Lu based the sensor on DNAzymes—DNA molecules that catalyze reactions as enzymes do. Many DNAzymes possess high affinity and specificity for metals, so Lu and his coworkers found a DNAzyme specific for the uranyl ion, UO₂²⁺, uranium's most common form in water. They then added a cleavage site, a fluorophore moiety, and two quencher moieties to suppress fluorescence. In the presence of UO₂²⁺, the DNAzyme chops off a part of the molecule containing the fluorophore, which then becomes a fluorescent beacon. With a detection limit of 11 ppt, the sensor rivals the most sensitive analytical instruments.